Coolant Dosing Device for Finely Dosing Liquefied Crygenic Gas

ABSTRACT

The invention relates to a coolant dosing device for the application of cryogenic gas for producing low temperatures as required e.g. in cryosurgery. The invention aims to ensure a disturbance-free operation in spite of often dirty gas and to exclude possible operating errors in the connection of capsules of the prior art. According to the invention, the coolant dosing device comprises a capillary tube that receives gas that has been filtered in the capsule and directly supplies it to the dispenser, thereby ensuring a disturbance-free operation. The low force connection between the capsule and the metering device by means of O-rings that are slipped over ensures a tight seal and an error-free operation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is an U.S. national phase application under 35 U.S.C. §371 based upon co-pending International Application No. PCT/IB2004/002127 filed on Jun. 27, 2004. Additionally, this U.S. national phase application claims the benefit of priority of co-pending International Application No. PCT/IB2004/002127 filed on Jun. 27, 2004. The entire disclosures of the prior applications are incorporated herein by reference. The international application was published on Feb. 2, 2006 under Publication No. WO2006/010971 A1.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a coolant dosing device of the liquid freezing system for cryogenic liquefied gas for producing low temperatures, for example in cryo-medicine.

2. Description of the Prior Art

Coolant dosing devices comprising a liquid freezing system are advantageous, because, during use, the gas consumption comes very close to the coolant demands required in theory. PCT 19958988.7 describes a coolant dosing device which, in an advantageous manner, by using small, gas-filled capsules offers very good mobility and is very efficient and practical in its handling.

However, the disadvantage of these dosing devices resides in the fact that their use is only possible in conjunction with commercially available capsules, because the gas inside the capsules contains, in part, substantial dirt particles. In addition thereto, the capsule needs to be pierced open mechanically by applying considerable force. This causes the formation of metal abrasion shavings having an increased negative impact on the existing filter.

Connecting the capsule to the dosing device must be done with the utmost care (with regard to the application force), if not, leakage may occur.

The sealing means in the region of the connecting zone are subject to extreme wear, since the capsule neck with its partially very rough surface properties is poorly suited for sealing. For physical and technical reasons the built-in filter in the coolant dosing device only offers a very small, effective filter surface. The accumulation of dirt particles at this location results in the so-called Joule Thomsen effect when liquefied cryogenic gas is passing through. The coolant dosing device is consequently rendered useless, because micro-sized ice crystal particles, which are formed as a result of the Joule Thomsen effect, clog the dispenser capillaries. Finally, when discharging the amount of residual gas, still present for technical reasons, in a gaseous state at the relatively high discharge velocity of the gas, additional, detaching dirt particles from the interior of the capsule impact negatively on the filter.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a coolant dosing device which does not suffer from the aforesaid drawbacks, which functions reliably and is of simple construction.

According to the invention, the object is attained by the features of patent claims.

Specific embodiments of the invention are described in the subsidiary claims. With the inventive solution, in particular with the mechanism for connecting the coolant dosing device to a capsule including a built-in valve, possible operational errors known per se, such as insufficient application force when sealing pressure capsules to the coolant dosing devices are prevented.

Moreover, the high risk of premature unscrewing of the pressure capsule and concomitant high-pressure emission of the gas are prevented, since the built-in valve in the capsule remains closed during unscrewing of the coolant dosing device with no gas being able to escape.

The built-in filter in the capsule is provided with an oversized filter surface so that no Joule Thomsen effect can occur.

In addition, the filter is in the operating position in the liquefied gas phase of the capsule, where the formation of a Joule Thomsen effect is not possible.

It is particularly advantageous that the filter has a port size of 5 μl, so that the emanating gas is practically germ-free.

The capsule with the built-in valve and filter is designed as a disposable item so that the question of wear of the valve and that of filter blockage may be neglected.

Due to the structurally simple design of the coolant dosing device and the possibility of its cleaning (simple blowing through the mobile capillary tube when dispenser is unscrewed) with cryogenic gas from the connected capsule, this device has an incomparably long serviceable life.

It is an advantageous concept of the invention that the coolant dosing device requires no filter for maintaining its functionality.

The commercially available devices need to constantly take into account filter replacements.

It is furthermore advantageous that in a simple manner, by means of screw-like threads, dispensers of any type may be connected by hand to the coolant dosing device, at the point of the gas discharge, and that these dispensers are reliably sealed on the high-polished capillary tube by an O-ring.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein:

FIG. 1 is a cross-section view of the coolant dosing device constructed in accordance with the principles of the present invention, with the phantom lines depicting environmental structure and forming no part of the claimed invention.

FIG. 2 is a cross-sectional view of the coolant dosing device of the present invention.

The same reference numerals refer to the same parts throughout the various figures.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings and particularly to FIGS. 1 and 2, a preferred embodiment of the coolant dosing device of the present invention is shown. The accompanying FIG. 1 shows a coolant dosing device according to the invention with a lever and its connecting component, a capsule with a valve, as well as a dosing device with a glass capillary tube nozzle and protective cover, shown in sectional view.

The accompanying FIG. 2 shows the coolant dosing device on a larger scale in sectional view. The coolant dosing device comprises a capillary tube 1, which on its closed side, in the direction of the capsule, has a port serving as the gas inlet 10.

With the movement AB of the lever 6, the slide 7, to which force is applied by the spring 5 and which is rigidly connected to the capillary tube 1, is moved in axial direction. As a result of this movement, after connection to the capsule with the valve of the capillary tube 1, brought about by way of a thread 4, it travels with its port 10 through an O-ring, positioned on the valve of the capsule and directed towards the valve plug of the capsule, thus opening the capsule. At port 10 the gas enters into the capillary tube 1, flowing in the direction 8 towards the connected dispenser which is screwed into the thread 9. The dispenser with its O-ring has pushed itself over the capillary tube 1 and is in efficiently sealed relationship thereon. 

1. A coolant dosing device for finely dosing a cryogenic liquefied gas, said coolant dosing device comprising: a capillary tube having an internal diameter of 0.2 to 0.8 mm, movable in the axial direction by means of a spring-loaded lever and is closed on one side and directly following thereon on the peripheral surface of the tube, has at least one port having a diameter of 0.1 to 0.6 mm mounted in a housing which comprises on each of its ends a thread for connecting a capsule with a valve and a dispenser with a nozzle.
 2. The coolant dosing device according to claim 1 wherein the capillary tube, which is shiftable in the axial direction, moves a valve plug in the capsule with its closed side, thus opening the capsule and that the gas of the capsule flows into the capillary tube via the port situated in the capillary tube and is transferred to the connected dispenser.
 3. (canceled)
 4. The coolant dosing device according to claim 1, wherein the capillary tube is a high-polished capillary tube which both when connecting the capsule with a valve and a filter as well as with a dispenser with a nozzle is in each case moved through an O-ring providing a very efficient sealing relationship when moved axially when opening and closing the valve.
 5. The coolant dosing device according to claim 1, wherein the coolant dosing device is adapted to discharge residual gas contained in the capsule.
 6. The coolant dosing device according to claim 1, wherein the capillary tube has an internal diameter of 0.7 mm.
 7. The coolant dosing device according to claim 1, wherein the at least one port has a diameter of 0.4 mm.
 8. A coolant dosing device comprising: a body having a first end connectable to a capsule with a valve, and a second end connectable to a dispenser; a capillary tube having a closed side defining a gas inlet port, in the direction of the capsule adjacent the first end of the body, the closed side being moveable within the body to cooperate with the valve of the capsule; a lever adapted to axially move a slide; and a spring rigidly connectable to the capillary tube, the spring being adapted to apply a force to the slide; wherein the capillary tube having an internal diameter of 0.2 to 0.8 mm; wherein the gas inlet port of the closed side of the capillary tube having a diameter of 0.1 to 0.6 mm.
 9. The coolant dosing device according to claim 8, wherein the capillary tube has an internal diameter of 0.7 mm.
 10. The coolant dosing device according to claim 8, wherein the at least one port has a diameter of 0.4 mm.
 11. The coolant dosing device according to claim 8, wherein the first end of the body is threaded and adapted to be connectable to the capsule, and wherein the second end of the body is threaded and adapted to be connectable to the dispenser.
 12. The coolant dosing device according to claim 8, wherein the closed side of the capillary tube is shiftable in the axial direction and adapted to move a valve plug in the capsule, thus opening the capsule and allowing gas in the capsule to flow into the capillary tube via the gas inlet port and then transferred to the connected dispenser.
 13. The coolant dosing device according to claim 8, wherein the spring is rigidly connectable to the capillary tube via a clamp ring. 